docs: def helical_turbulent_fd_Srinivasan(Re, Di, Dc):
      r'''Calculates Darcy friction factor for a fluid flowing inside a curved 
      pipe such as a helical coil under turbulent conditions, using the method of 
      Srinivasan [1]_, as shown in [2]_ and [3]_.
      
      .. math::
          f_d = \frac{0.336}{{\left[Re\sqrt{\frac{D_i}{D_c}}\right]^{0.2}}}
  
      Parameters
      ----------
      Re : float
          Reynolds number with `D=Di`, [-]
      Di : float
          Inner diameter of the coil, [m]
      Dc : float
          Diameter of the helix/coil measured from the center of the tube on one
          side to the center of the tube on the other side, [m]
  
      Returns
      -------
      fd : float
          Darcy friction factor for a curved pipe [-]
  
      Notes
      -----    
      Valid for 0.01 < Di/Dc < 0.15, with no Reynolds number criteria given in
      [2]_ or [3]_.
      
      [2]_ recommends this method, using the transition criteria of Srinivasan as
      well. [3]_ recommends using either this method or the Ito method. This
      method did not make it into the popular review articles on curved flow.
  
      Examples
      --------
      >>> helical_turbulent_fd_Srinivasan(1E4, 0.01, .02)
      0.0570745212117107
  
      References
      ----------
      .. [1] Srinivasan, PS, SS Nandapurkar, and FA Holland. "Friction Factors 
         for Coils." TRANSACTIONS OF THE INSTITUTION OF CHEMICAL ENGINEERS AND
         THE CHEMICAL ENGINEER 48, no. 4-6 (1970): T156
      .. [2] Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: 
         Van Nostrand Reinhold Co., 1984.
      .. [3] Rohsenow, Warren and James Hartnett and Young Cho. Handbook of Heat
         Transfer, 3E. New York: McGraw-Hill, 1998.
      '''
      De = Dean(Re=Re, Di=Di, D=Dc)
      return 0.336*De**-0.2